[Note: the full text of this free access article, linking reduced heart rate responsiveness to cognitive impairment in CFS, is available HERE.]

Abstract:Background: Cognitive difficulties and autonomic dysfunction have been reported separately in patients with chronic fatigue syndrome (CFS). A role for heart rate variability (HRV) in cognitive flexibility has been demonstrated in healthy individuals, but this relationship has not as yet been examined in CFS. The objective of this study was to examine the relationship between HRV and cognitive performance in patients with CFS.

Methods: Participants were 30 patients with CFS and 40 healthy controls; the groups were matched for age, sex, education, body mass index, and hours of moderate exercise/week. Questionnaires were used to obtain relevant medical and demographic information, and assess current symptoms and functional impairment. Electrocardiograms, perceived fatigue/effort and performance data were recorded during cognitive tasks. Between-group differences in autonomic reactivity and associations with cognitive performance were analysed.

Results: Patients with CFS showed no deficits in performance accuracy, but were significantly slower than healthy controls. CFS was further characterized by low and unresponsive HRV; greater heart rate (HR) reactivity and prolonged HR-recovery after cognitive challenge. Fatigue levels, perceived effort and distress did not affect cognitive performance. HRV was consistently associated with performance indices and significantly predicted variance in cognitive outcomes.

Conclusions: These findings reveal for the first time an association between reduced cardiac vagal tone and cognitive impairment in CFS and confirm previous reports of diminished vagal activity.

Source: PloS One, Nov 14, 2012. By Beaumont Alison, Burton AR, Lemon J, Bennett BK, Lloyd A, vollmer-Conna U. School of Psychiatry, University of New South Wales, Sydney, New South Wales, Australia; School of Medical Sciences, University of New South Wales, Sydney; Department of Medical Oncology, Prince of Wales Hospital, Sydney; Inflammation and Infection Research Centre, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia. [E-mail: ute@unsw.edu.au]